A hands-on tour of how real systems are built, from a single box to globe-spanning infrastructure. Every chapter is a live, interactive deep-dive you can poke at.
The mental models before any box gets drawn.
What you'll build. Grow one server into a fleet, one bottleneck at a time.
What you'll build. Get to the right order of magnitude in your head, fast.
What you'll build. A repeatable 4-step process so you're never staring at a blank whiteboard.
What you'll build. What you must give up when the network breaks — and even when it doesn't.
Reusable primitives you'll assemble into everything else.
What you'll build. Say "slow down" fairly, cheaply, at scale.
What you'll build. Add or remove a server without reshuffling everything.
What you'll build. Build a distributed, fault-tolerant store from first principles.
What you'll build. Hand out billions of sortable IDs with no central bottleneck.
What you'll build. The append-only log that decouples everything (a mini-Kafka).
What you'll build. Push data to clients the instant it changes.
The interview greatest hits, built end to end.
What you'll build. Turn a long link into seven characters and back.
What you'll build. Politely walk the entire web without getting stuck.
What you'll build. Fan one event out to push, SMS, and email reliably.
What you'll build. Assemble a personalized timeline for millions.
What you'll build. Real-time messaging with presence and delivery receipts.
What you'll build. Suggest the top completions in under 100ms.
What you'll build. Upload, transcode, and stream video at planet scale.
What you'll build. Sync files across devices without re-uploading everything.
The problems that show up in 2026 interviews.
What you'll build. Find what's near you, and who, in real time.
What you'll build. Count billions of events in near-real-time.
What you'll build. Move money exactly once and prove it later.
What you'll build. Let many people edit one doc and always converge.
The category the 2020 playbook never had.